Summary: This project relates to the investigation of an in vitro ELISA potency assay to replace the guinea pig death test portion of the official release test for the tetanus component in vaccines. Reports of an ELISA method in the literature, and the use of this method in the laboratory are dependent on a source of purified Tetanus Toxin. Preliminary data and proposals for an international collaborative study were discussed at a meeting in June 2000. There has been no further investigation of the correlation between animal and laboratory tests this year due to problems with the supply of the purified Tetanus reagent.